Antistatic styrenic polymer composition

ABSTRACT

The invention relates to a composition comprising, for 100 parts by weight, 99-60 parts of a styrenic polymer (A), 1-40 parts of (B)+(C), (B) being a polyamide block and polyether block copolymer essentially comprising ethylene oxide patterns (C2H4-O)—, (C) being a compatibilizer chosen from block copolymers comprising at least one polymerized block comprising styrene and at elast one polymerized block comprising methyl methacrylate, (B)/(C) ranging from 2 to 10.

The present invention relates to antistatic styrenic polymercompositions and more specifically to a composition comprising astyrenic polymer (A), a copolymer (B) containing polyamide blocks andpolyether blocks comprising essentially ethylene oxide units —(C₂H₄—O)—,and a compatibilizer (C).

The aim of the invention is to give the styrenic polymer (A) antistaticproperties. The formation and retention of static-electricity charges onthe surface of most plastics are known. The presence of staticelectricity on thermoplastic films results, for example, in these filmssticking to one another, making them difficult to separate. The presenceof static electricity on packaging films may cause the accumulation ofdust on the articles to be packaged and thus impede their use. Styrenicresins, such as polystyrene or ABS, are used to make cases forcomputers, for telephones, for televisions, for photocopiers, and fornumerous other articles. Static electricity causes accumulation of dustbut most importantly can also cause damage to microprocessors orconstituents of electronic circuits present in these articles. For theseapplications, it is generally desirable to find compositions based onstyrenic resin whose surface resistivity is below 5.10¹³ Ω/□ measured tothe standard IEC93 or whose volume resistivity is below 5.10¹⁶ Ω.cmmeasured to the standard IEC93 (the type of resistivity being chosen asa function of the application, given that these two types of resistivityalways increase in the same direction) . This is based on theconsideration that these resistivities provide adequate antistaticproperties for certain applications in the field of polymer materials incontact with electronic components.

The prior art has described antistatic agents, such as ionic surfactantsof ethoxylated amine type or sulfonate type which are added withinpolymers. However, the antistatic properties of the polymers depend onambient humidity and are not permanent, since these agents migrate tothe surface of the polymers and disappear. Copolymers containinghydrophilic polyether blocks and polyamide blocks have therefore beenproposed as antistatic agents, these agents having the advantage of notmigrating and therefore of providing antistatic properties which arepermanent and less dependent on ambient humidity.

The Japanese patent application JP 60 170 646 A, published Sep. 4, 1985,describes compositions consisting of from 0.01 to 50 parts of polyetherblock amide and 100 parts of polystyrene, these being used to makesliding parts and wear-resistant parts. The antistatic properties arenot mentioned.

Patent application EP 167 824, published Jan. 15, 1986, describescompositions similar to the preceding compositions, and according to oneembodiment of the invention the polystyrene may be blended with apolystyrene functionalized by an unsaturated carboxylic anhydride. Thesecompositions are used to make injection-molded parts. The antistaticproperties are not mentioned.

The Japanese patent application JP 60 023 435 A, published Feb. 6, 1985,describes antistatic compositions comprising from 5 to 80% ofpolyetheresteramides and from 95 to 20% of a thermoplastic resin chosenfrom, inter alia, polystyrene, ABS and PMMA, this resin beingfunctionalized by acrylic acid or maleic anhydride. The amount ofpolyetheresteramide in the examples is 30% by weight of thecompositions.

The patent EP 242 158 describes antistatic compositions comprising from1 to 40% of polyetheresteramide and from 99 to 60% of a thermoplasticresin chosen from styrenic resins, PPO and polycarbonate. According to apreferred embodiment, the compositions also comprise a vinyl polymerfunctionalized by a carboxylic acid, one example being a polystyrenemodified by methacrylic acid.

The international patent application PCT/FR00/02140 teaches the use ofcopolymers of styrene and of an unsaturated carboxylic anhydride,copolymers of ethylene and of an unsaturated carboxylic anhydride,copolymers of ethylene and of an unsaturated epoxide, block copolymersin the form of SBS or SIS grafted with a carboxylic acid or anunsaturated carboxylic anhydride, as compatibilizer between a styrenicresin and a copolymer containing polyamide blocks and polyether blocks.

Other prior-art documents which may be cited are:

-   -   EP 927727,    -   J. Polym. Sci., Part C: Polym. Lett. (1989), 27(12), 481    -   J. Polym. Sci., Part B, Polym. Phys. (1996), 34(7), 1289    -   JAPS, (1995), 58(4), 753    -   JP 04370156    -   JP 04239045    -   JP 02014232    -   JP 11060855    -   JP 11060856    -   JP 09249780    -   JP 08239530    -   JP 08143780

The prior art demonstrates either blends (i) of styrenic resin andpolyetheresteramide without compatibilizer or blends (ii) ofpolyetheresteramide and functionalized styrenic resin or else blends(iii) of polyetheresteramide, non-functionalized styrenic resin andfunctionalized styrenic resin.

The blends (i) are antistatic if the polyetheresteramide is carefullychosen, but have poor mechanical properties, elongation at break inparticular being much lower than that of the styrenic resin alone. Asfar as the blends (ii) and (iii) are concerned, it is necessary to haveaccess to a functionalized styrenic resin, and this is a complicated andcostly matter. The object of the invention is to provide antistaticproperties to the ordinary styrenic resins used to make theabovementioned articles, these being non-functionalized resins. It hasnow been found that when particular compatibilizers are used it ispossible to obtain styrenic resin compositions which comprise a styrenicresin and a copolymer containing polyamide blocks and polyether blocks,and which have excellent elongation at break, excellent tensile strengthand excellent impact resistance (Charpy notched), when compared with thesame composition without compatibilizer.

The present invention provides a composition comprising per 100 parts byweight:

-   -   from 99 to 60 parts by weight of a styrenic polymer (A),    -   from 1 to 40 parts by weight of (B)+(C), (B) being a copolymer        containing polyamide blocks and polyether blocks comprising        essentially ethylene oxide units —(C₂H₄—O)—, and (C) being a        compatibilizer chosen from block copolymers comprising at least        one polymerized block comprising styrene and at least one        polymerized block comprising methyl methacrylate, the (B)/(C)        ratio by weight being between 2 and 10.

By way of example of styrenic polymer (A) mention may be made ofpolystyrene, polystyrene modified by elastomers, random or blockcopolymers of styrene and of dienes such as butadiene, copolymers ofstyrene and of acrylonitrile (SAN), SAN modified by elastomers, inparticular ABS, obtained, for example, by grafting (graftpolymerization) of styrene and acrylonitrile on a graft-base composed ofpolybutadiene or of butadiene-acrylonitrile copolymer, and blends of SANand of ABS. The abovementioned elastomers may be, for example, EPR(abbreviation for ethylene-propylene rubber or ethylene-propyleneelastomer), EPDM (abbreviation for ethylene-propylene-diene rubber orethylene-propylene-diene elastomer), polybutadiene,acrylonitrile-butadiene copolymer, polyisoprene, isoprene-acrylo-nitrilecopolymer. In particular, A may be an impact polystyrene comprising amatrix of polystyrene surrounding rubber nodules generally comprisingpolybutadiene.

In the abovementioned polymers (A), part of the styrene may be replacedby unsaturated monomers copolymerizable with styrene, and by way ofexample mention may be made of alpha-methylstyrene and the (meth)acrylicesters. In this case, A may comprise a copolymer of styrene, among whichmention may be made of styrene-alpha-methylstyrene copolymers,styrene-chlorostyrene copolymers, styrene-propylene copolymers,styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-vinylchloride copolymers, styrene-vinyl acetate copolymers, styrene-alkylacrylate copolymers (methyl acrylate, ethyl acrylate, butyl acrylate,octyl acrylate, phenyl acrylate), styrene-alkyl methacrylate copolymers(methyl methacrylate, ethyl methacrylate, butyl methacrylate, phenylmethacrylate), styrene-methyl chloroacrylate copolymers andstyrene-acrylonitrile-alkyl acrylate copolymers. The content ofcomonomers in these polymers is generally up to 20% by weight. Thepresent invention also provides high-melting-point metallocenepolystyrenes.

Without exceeding the scope of the invention, (A) could be a blend oftwo or more of the preceding polymers.

The styrenic polymer A preferably comprises more than 50% by weight ofstyrene. If the styrenic polymer is SAN, it preferably contains morethan 75% by weight of styrene.

The polymers (B) containing polyamide blocks and polyether blocks arethe result of copolycondensation of terminally reactive polyamidesequences with terminally reactive polyether sequences, examples being,inter alia:

-   -   1) Polyamide sequences having diamine chain ends with        polyoxyalkylene sequences having dicarboxylic chain ends.    -   2) Polyamide sequences having dicarboxylic chain ends with        polyoxyalkylene sequences having diamine chain ends and obtained        via cyanoethylation and hydrogenation of        alpha-omega-dihydroxylated aliphatic polyoxyalkylene sequences        known as polyetherdiols.    -   3) Polyamide sequences having dicarboxylic chain ends with        polyetherdiols, the products obtained in this particular case        being polyetheresteramides. The copolymers (B) are        advantageously of this type.

The polyamide sequences having dicarboxylic chain ends derive, forexample, from the condensation of alpha-omega-aminocarboxylic acids, oflactams or of dicarboxylic acids and diamines in the presence of adicarboxylic acid as chain regulator.

The number-average molecular weight Mn of the polyamide sequences isbetween 300 and 15 000 and preferably between 600 and 5000. The weightMn of the polyether sequences is between 100 and 6000 and preferablybetween 200 and 3000.

The polymers containing polyamide blocks and polyether blocks may alsocomprise units having random distribution. These polymers may beprepared via simultaneous reaction of the polyether and of theprecursors of the polyamide blocks.

For example, a reaction may be carried out using polyetherdiol, a lactam(or an alpha-omega-amino acid) and a diacid chain regulator in thepresence of a little water. This gives a polymer having essentiallypolyether blocks and polyamide blocks of very variable length, and alsohaving the various reactants randomly distributed along the polymerchain, having reacted in random fashion.

These polymers containing polyamide blocks and polyether blocks whichderive from the copolycondensation of polyamide sequences and polyethersprepared previously or from a one-step reaction have, for example, ShoreD hardnesses which can be between 20 and 75 and advantageously between30 and 70 and have intrinsic viscosity between 0.8 and 2.5 measured inmeta-cresol at 250° C. for an initial concentration of 0.8 g/100 ml. TheMFIs may be between 5 and 50 (235° C. under a load of 1 kg)

The polyetherdiol blocks are either used as they stand andcopolycondensed with the carboxylic-terminated polyamide blocks or areaminated and then converted to polyetherdiamines and condensed with thecarboxylic-terminated polyamide blocks. They may also be mixed withprecursors of polyamide and a chain regulator to make polymerscontaining polyamide blocks and polyether blocks having randomlydistributed units.

Polymers containing polyamide blocks and polyether blocks are describedin the patents U.S. Pat. Nos. 4,331,786, 4,115,475, 4,195,015,4,839,441, 4,864,014, 4,230,838 and 4,332,920.

In a first embodiment of the invention, the polyamide sequences havingdicarboxylic chain ends derive, for example, from the condensation ofalpha-omega-amino-carboxylic acids, of lactams or of dicarboxylic acidsand diamines in the presence of a dicarboxylic acid chain regulator. Byway of example of alpha-omega-aminocarboxylic acids, mention may be madeof aminoundecanoic acid, and by way of example of a lactam mention maybe made of caprolactam and laurolactam, and by way of example ofdicarboxylic acid mention may be made of adipic acid, decanedioic acidand dodecanedioic acid, and by way of example of diamine mention may bemade of hexamethylenediamine. The polyamide blocks are advantageouslycomposed of nylon-12 or of nylon-6. The melting point of these polyamidesequences, which is also that of the copolymer (B), is generally from 10to 15° C. below that of PA 12 or of PA 6.

Depending on the nature of (A), it can be useful to use a copolymer (B)whose melting point is less high in order to avoid degrading (A) duringthe incorporation of (B), and this is the subject of the second andthird embodiment of the invention below.

In a second embodiment of the invention, the polyamide sequences are theresult of condensation of one or more alpha-omega-aminocarboxylic acidsand/or of one or more lactams having from 6 to 12 carbon atoms in thepresence of a dicarboxylic acid having from 4 to 12 carbon atoms, andare of low weight, i.e. Mn from 400 to 1000. By way of example ofalpha-omega-amino-carboxylic acid mention may be made of aminoundecanoicacid and aminododecanoic acid. By way of example of dicarboxylic acidmention may be made of adipic acid, sebacic acid, isophthalic acid,butanedioic acid, cyclohexane-1,4-dicarboxylic acid, terephthalic acid,the sodium or lithium salt of sulfoisophthalic acid, dimerized fattyacids (these dimerized fatty acids having a dimer content of at least98% by weight and preferably being hydrogenated) and dodecanedioic acidHOOC—(CH₂)₁₀—COOH.

By way of example of lactam, mention may be made of caprolactam andlaurolactam.

Caprolactam should be avoided unless the polyamide is purified byremoving the caprolactam monomer which remains dissolved within it.

Polyamide sequences obtained via condensation of laurolactam in thepresence of adipic acid or of dodecanedioic acid and having a weight{overscore (Mn)} of 750 have a melting point of 127-130° C.

In a third embodiment of the invention, the polyamide sequences are theresult of condensation of at least one alpha-omega-aminocarboxylic acid(or one lactam), at least one diamine and at least one dicarboxylicacid. The alpha-omega-aminocarboxylic acid, the lactam and thedicarboxylic acid may be chosen from those mentioned above.

The diamine may be an aliphatic diamine having from 6 to 12 atoms, or itmay be an acrylic and/or saturated cyclic diamine.

By way of examples mention may be made of hexa-methylenediamine,piperazine, 1-aminoethylpiperazine, bisaminopropylpiperazine,tetramethylenediamine, octa-methylenediamine, decamethylenediamine,dodecamethylenediamine, 1,5-diaminohexane,2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophoronediamine(IPD), methylpentamethylenediamine (MPDM), bis (amino-cyclohexyl)methane(BACM), bis (3-methyl-4-aminocyclohexyl)methane (BMACM).

In the second and third embodiment of the invention, the variousconstituents of the polyamide sequence and their proportion are chosenin order to obtain a melting point below 150° C. and advantageouslybetween 90 and 135° C. Low-melting-point copolyamides are described inthe patents U.S. Pat. No. 4,483,975, DE 3 730 504, U.S. Pat. No.5,459,230. The same proportions of the constituents are utilized for thepolyamide blocks of (B) . (B) may also be the copolymers described inU.S. Pat. No. 5,489,667.

The polyether blocks may represent from 5 to 85% by weight of (B) . Thepolyether blocks may contain units other than the ethylene oxide units,e.g. units of propylene oxide or of polytetrahydrofuran (which leads topolytetramethylene glycol sections within the chain). Simultaneous usemay also be made of PEG blocks, i.e. blocks consisting of ethylene oxideunits, PPG blocks, i.e. blocks consisting of propylene oxide units, andPTMG blocks, i.e. blocks consisting of tetramethylene glycol units, alsotermed polytetrahydrofuran. Use is advantageously made of PEG blocks orof blocks obtained by ethoxylation bisphenols, e.g. bisphenol A. Theselatter products are described in patent EP 613 919. The amount ofpolyether blocks in (B) is advantageously from 10 to 50% by weight of(B) and preferably from 35 to 50%.

The copolymers of the invention may be prepared by any means permittinglinkage of the polyamide blocks to the polyether blocks. Essentially,two processes are used in practice, one being a two-step process and theother being a single-step process.

The two-step process consists firstly in preparing thecarboxylic-terminated polyamide blocks via condensation of precursors ofpolyamide in the presence of a dicarboxylic acid chain regulator, andthen, in a second step, in adding the polyether and a catalyst. If theprecursors of polyamide are only lactams or alpha-omega-aminocarboxylicacids, a dicarboxylic acid is added. If the precursors themselvescomprise a dicarboxylic acid it is used in excess with respect to thestoichiometry of the diamines. The reaction usually takes place between180 and 300° C., preferably from 200 to 260° C., the pressure developingin the reactor being between 5 and 30 bar, and being maintained forabout 2 hours. The pressure is slowly reduced to atmospheric pressureand then the excess water is distilled off, for example for one or twohours.

Once the carboxylic-terminated polyamide has been prepared, thepolyether and a catalyst are then added. The polyether may be added inone or more portions, and the same applies to the catalyst. In oneadvantageous embodiment, the polyether is added first, and the reactionof the terminal OH groups of the polyether and of the terminal COOHgroups of the polyamide begins with formation of ester bonds andelimination of water; water is removed as far as possible from thereaction mixture by distillation, and then the catalyst is introduced inorder to obtain the bond between the amide blocks and the polyetherblocks. This second step is carried out with stirring, preferably undera vacuum of at least 5 mm of Hg (650 Pa) at a temperature such that thereactants and the copolymers obtained are molten. By way of example,this temperature may be between 100 and 400° C. and mostly between 200and 300° C. The reaction is followed by measuring the torque exerted bythe molten polymer on the stirrer or by measuring the electrical powerconsumed by the stirrer. The end of the reaction is determined by thetorque value or target power value. The catalyst is defined as being anymaterial making it easier to bond the polyamide blocks to the polyetherblocks via esterification. The catalyst is advantageously a derivativeof a metal (M) chosen from the group formed by titanium, zirconium andhafnium.

By way of example of a derivative mention may be made of thetetraalkoxides complying with the general formula M(OR) ₄, in which Mrepresents titanium, zirconium or hafnium and R, identical or different,indicate linear or branched alkyl radicals having from 1 to 24 carbonatoms.

Examples of the C₁-C₂₄-alkyl radicals among which the radicals R arechosen for the tetraalkoxides used as catalysts in the process accordingto the invention are methyl, ethyl, propyl, isopropyl, butyl,ethylhexyl, decyl, dodecyl, hexadodecyl. The preferred catalysts are thetetraalkoxides for which the radicals R, identical or different, are theC₁-C₈-alkyl radicals. Particular examples of these catalysts areZr(OC₂H₅)₄, Zr(O-isoC₃H₇)₄, Zr(OC₄H₉)₄, Zr(OC₅H₁₁)₄, Zr(OC₆H₁₃)₄,Hf(OC₂H₅)₄, Hf(OC₄H₉)₄, Hf(O-isoC₃H₇)₄.

The catalyst used in the process according to the invention may consistsolely of one or more tetraalkoxides defined above of formula M(OR)₄. Itmay also be formed by combining one or more of these tetraalkoxides withone or more alcoholates of alkali metals or of alkaline earth metalshaving the formula (R₁O)_(p)Y in which R₁ indicates a hydrocarbonradical, advantageously a C₁-C₂₄-alkyl radical, and preferably aC₁-C₈-alkyl radical, Y represents an alkali metal or alkaline earthmetal, and p is the valency of Y. The amounts of alcoholate of alkalimetal or of alkaline earth metal and of tetraalkoxides of zirconium orof hafnium that are combined to constitute the mixed catalyst may varywithin wide limits. However, it is preferable to use amounts ofalcoholate and of tetraalkoxides such that the molar proportion ofalcoholate is approximately equal to the molar proportion oftetraalkoxide.

The proportion by weight of catalyst, i.e. of the tetraalkoxide(s) ifthe catalyst does not include alcoholate of alkali metal or of alkalineearth metal, or else of the entirety of the tetraalkoxide(s) and of thealcoholate(s) of alkali metal or of alkaline earth metal if the catalystis formed by combining these two types of compound, advantageouslyvaries from 0.01 to 5% by weight of the mixture of the dicarboxylicpolyamide with the polyoxyalkylene glycol, and is preferably between0.05 and 2% of that weight.

By way of example of other derivatives, mention may also be made of thesalts of the metal (M), in particular the salts of (M) with an organicacid and the complex salts of the oxide of (M) and/or the hydroxide of(M) with an organic acid. The organic acid may advantageously be formicacid, acetic acid, propionic acid, butyric acid, valeric acid, caproicacid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearicacid, oleic acid, linoleic acid, linolenic acid, cyclohexanecarboxylicacid, phenyl-acetic acid, benzoic acid, salicylic acid, oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid,fumaric acid, phthalic acid and crotonic acid. Acetic and propionicacids are particularly preferred. M is advantageously zirconium. Thesesalts may be termed zirconyl salts. Without being bound by thisexplanation, the Applicant thinks that these salts of zirconium with anorganic acid or the complex salts mentioned above release ZrO⁺⁺ duringthe course of the process. Use is made of the product sold as zirconylacetate. The amount to use is the same as that for the M(OR)₄derivatives.

This process and these catalysts are described in the patents U.S. Pat.Nos. 4,332,920, 4,230,838, 4,331,786, 4,252,920, JP 07145368A, JP06287547A and EP 613919.

With respect to the single-step process, all the reactants used in thetwo-step process are mixed, i.e. the precursors of polyamide, thedicarboxylic acid chain regulator, the polyether and the catalyst. Thereactants and the catalyst are the same as those in the two-step processdescribed above. If the precursors of polyamide are only lactams, it isadvantageous to add a little water.

The copolymer essentially has the same polyether blocks and the samepolyamide blocks, but also has a small fraction of the various reactantsrandomly distributed along the polymer chain, having reacted in randomfashion.

The reactor is closed and heated, with stirring, as in the first step ofthe two-step process described above. The pressure that develops isbetween 5 and 30 bar. Once the pressure increase has concluded, reducedpressure is applied to the reactor while maintaining vigorous stirringof the molten reactants. The reaction is followed as above for thetwo-step process.

The catalyst used in this one-step process is preferably a salt of themetal (M) with an organic acid or a complex salt of the oxide of (M)and/or the hydroxide of (M) with an organic acid.

The ingredient (B) may also be a polyetheresteramide (B) havingpolyamide blocks comprising sulfonates of dicarboxylic acids either aschain regulators for the polyamide block or in association with adiamine as one of the monomers constituting the polyamide block, andhaving polyether blocks essentially consisting of alkylene oxide units,as described in the international application PCT/FR00/02889.

The compatibilizer C may be any block copolymer comprising at least onepolymerized block comprising styrene and at least one polymerized blockcomprising methyl methacrylate.

The polymerized block comprising styrene is generally present in C in aproportion of from 20 to 80% by weight.

The polymerized block comprising methyl methacrylate is generallypresent in C in a proportion of from 20 to 80% by weight.

The polymerized block comprising styrene generally has a glasstransition temperature above 100° C. and preferably comprises at least50% by weight of styrene. The polymerized block comprising styrene mayalso comprise an unsaturated epoxide (obtained by copolymerization),this latter preferably being glycidyl methacrylate. The unsaturatedepoxide may be present in a proportion of from 0.01% to 5% by weight inthe polymerized block comprising styrene.

The polymerized block comprising methyl methacrylate generally has aglass transition temperature above 100° C. and preferably comprises morethan 50% by weight of methyl methacrylate. The polymerized blockcomprising methyl methacrylate may also comprise an unsaturated epoxide(obtained by copolymerization), this latter preferably being glycidylmethacrylate. The unsaturated epoxide may be present in a proportion offrom 0.01% to 5% by weight in the polymerized block comprising methylmethacrylate.

The block copolymer comprising at least one polymerized block comprisingstyrene and at least one polymerized block comprising methylmethacrylate may also be grafted with an unsaturated epoxide, preferablyglycidyl methacrylate.

By way of example of unsaturated epoxide, mention may be made of:

-   -   the aliphatic glycidyl esters and aliphatic glycidyl ethers,        such as allyl glycidyl ether, vinyl glycidyl ether, glycidyl        maleate and glycidyl itaconate, and glycidyl (meth)acrylate, and    -   the alicyclic glycidyl esters and alicyclic glycidyl ethers,        such as 2-cyclohexene glycidyl ether, diglycidyl        cylohexene-4,5-dicarboxylate, glycidyl        cyclohexene-4-carboxylate, glycidyl        2-methyl-5-norbornene-2-carboxylate and diglycidyl        cis-endo-bicyclo[2.2.1]-5-heptene-2,3-di-carboxylate.

In the block comprising styrene, part of the styrene may be replaced byunsaturated monomers copolymerizable with styrene, and by way of examplemention may be made of alpha-methylstyrene and the (meth)acrylic esters.In this case, the block comprising styrene is a copolymer of styrene,among which mention may be made of styrene-alpha-methylstyrenecopolymers, styrene-chlorostyrene copolymers, styrene-butadienecopolymers, styrene-isoprene copolymers, styrene-vinyl chloridecopolymers, styrene-vinyl acetate copolymers, styrene-alkyl acrylatecopolymers (methyl acrylate, ethyl acrylate, butyl acrylate, octylacrylate, phenyl acrylate), styrene-alkyl methacrylate copolymers(methyl methacrylate, ethyl methacrylate, butyl methacrylate, phenylmethacrylate), styrene-methyl chloroacrylate copolymers andstyrene-acrylonitrile-alkyl acrylate copolymers.

In particular, C may be:

-   -   a diblock copolymer comprising a block of a polymer of styrene        and a block of a polymer of methyl methacrylate;    -   a diblock copolymer comprising a block of a polymer of styrene        and a block of poly (methyl methacrylate-co-glycidyl        methacrylate);    -   a diblock styrene polymer-methyl methacrylate polymer copolymer,        said copolymer being grafted with glycidyl methacrylate;    -   a diblock copolymer comprising a homopolystyrene block and a        homopolymethyl methacrylate block;    -   a diblock copolymer comprising a homopolystyrene block and a        block of poly(methyl methacrylate-co-glycidyl methacrylate);    -   a diblock homopolystyrene-homopolymethyl meth-acrylate        copolymer, said copolymer being grafted with glycidyl        methacrylate;    -   a diblock copolymer comprising a block of        polystyrene-co-glycidyl methacrylate and a block of polymethyl        methacrylate;    -   a diblock copolymer comprising a block of        polystyrene-co-glycidyl methacrylate and a block of poly (methyl        methacrylate-co-glycidyl methacrylate).

C may moreover also be a triblock S-B-M copolymer, S representing thepolymerized block comprising styrene, M representing the polymerizedblock comprising methyl methacrylate, and B representing an elastomericblock having a glass transition temperature (Tg) below 5° C., preferablybelow 0° C. and more preferably below −40° C. The monomer used tosynthesize the elastomeric block B may be a diene chosen from butadiene,isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene,2-phenyl-1,3-butadiene. B is advantageously chosen from thepoly(dienes), in particular poly(butadiene), poly(isoprene) and theirrandom copolymers, or else from the partially or completely hydrogenatedpoly(dienes). Among the polybutadienes, it is advantageous to use thosewhose Tg is lowest, e.g. 1,4-polybutadiene with Tg (about −90° C.) lowerthan that of 1,2-polybutadiene (about 0° C.). The blocks B may also behydrogenated. This hydrogenation is carried out by the usual methods.

The monomer used to synthesize the elastomeric block B may also be analkyl (meth)acrylate, giving the following Tg values in bracketsfollowing the name of the acrylate: ethyl acrylate (−24° C.), butylacrylate (−54° C.), 2-ethylhexyl acrylate (−85° C.), hydroxyethylacrylate (−15° C.) and 2-ethylhexyl methacrylate (−10° C.). Butylacrylate is advantageously used.

The blocks B preferably consist mainly of 1,4-poly-butadiene.

C may therefore be:

-   -   an S-B-M triblock copolymer in which S is a block of a polymer        of styrene, B is a block of polybutadiene, and M is a block of a        polymer of methyl methacrylate;    -   an S-B-M triblock copolymer in which S is a block of        homopolystyrene, B is a block of polybutadiene, and M is a block        of homopolymethyl methacrylate.

Within the scope of the invention is it possible to use one or morecompatibilizers C.

The compatibilizer C may in particular be prepared by controlledfree-radical polymerization methods in the presence of a stable freeradical (generally a nitroxide) following the principle of the teachingof EP 927727. The SBMs may be obtained by an anionic route.

The level of antistatic properties increases with the proportion of (B)and, for equal amounts of (B), with the proportion of ethylene oxideunits present in (B).

According to the application, preference will be given to including aproportion of (B) sufficient to obtain, in the final composition, asurface resistivity below 5.10¹³ Ω/□ measured to the standard IEC93.According to the application, preference will be given to including aproportion of (B) sufficient to give the final composition a volumeresistivity below 5.10¹⁶ Ω.cm measured to the standard IEC93.

The amount of (B)+(C) is advantageously from 5 to 30 parts per 95-70parts of (A) and preferably from 10 to 20 per 90-80 parts of (A). The(B)/(C) ratio is advantageously between 4 and 10. The amount of C in thecomposition may be from 0.5 to 5 parts by weight per 100 parts by weightof composition.

Within the scope of the invention it is possible to add mineral fillers(talc, CaCO₃, kaolin, etc.), reinforcing agents (glass fiber, mineralfiber, carbon fiber, etc.), stabilizers (heat, UV), flame retardants andcolorants.

The compositions of the invention are prepared by the methods usual forthermoplastics, e.g. by extrusion or with the aid of twin-screw mixers.

The present invention also provides the articles manufactured with thepreceding compositions; examples of these are films, pipes, sheets,packaging, cases for computers, for fax machines or for telephones.

The following abbreviations are used in the examples below:

-   -   GMA: glycidyl methacrylate;    -   MAM: methyl methacrylate;    -   SM: polystyrene-block-polymethyl methacrylate;    -   SM/GMA: polystyrene-block-polymethyl methacrylate        grafted/copolymerized with glycidyl methacrylate;    -   PEG: polyethylene glycol;    -   PMMA: polymethyl methacrylate;    -   Mw: weight-average molecular weight;    -   Mn: number-average molecular weight;    -   Mw/Mn: polydispersity    -   Rv: volume resistivity (Ω.cm)    -   Rs: surface resistivity (Ω/□)    -   HO-TEMPO: 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy usually        marketed as 4-hydroxy TEMPO;    -   SEC: steric exclusion chromatography;    -   LAC: liquid adsorption chromatography;    -   GPC: gel permeation chromatography;    -   NMR: nuclear magnetic resonance;    -   TEM: transmission electron microscopy.

The following ingredients are used in the examples below:

-   -   PS 4241: styrene-butadiene copolymer. This copolymer has a flow        index of between 3 and 5 g/10 min at 200° C. under 5 kg        (standard ISO 1133:91). It is also characterized by a Vicat        point of 97° C. (standard ISO 306A50). This copolymer has a        styrene content of about 95% by weight. This copolymer is        marketed by ATOFINA with the trademark Lacqrene.    -   MH1657: copolyether-block-amide having nylon-6 blocks of        number-average molecular weight 1500 and PEG blocks of        number-average molecular weight 1500; the melting point is        204° C. This copolymer is marketed by ATOFINA with the trademark        Pebax MH1657.    -   SM: this is a polystyrene-block-(polymethyl methacrylate) block        copolymer prepared by controlled free-radical polymerization,        with Mw=106 000 and polydispersity of 2.1. The proportion of        styrene is 61% by weight.    -   SM/GMA: this is a polystyrene-block-(methyl        methacrylate-co-glycidyl methacrylate) block copolymer prepared        by controlled free-radical polymerization, with Mw=108 700 and        polydispersity of 2.0. The proportion of styrene is 65% by        weight, and it contains 0.4% by weight of GMA.

The following characterization methods were used in the examples below:

Mechanical Properties:

The compositions obtained are injection-molded at temperatures of from220 to 240° C. in the form of dumbbells, bars or plaques. The dumbbellspermit the ISO R527 tensile tests to be carried out and the bars areused for the Charpy notched impact to the standard ISO 179:93 leA.

Antistatic Properties:

Plaques of the following dimensions 100×100 ×2 mm³ are injection-moldedand permit the IEC-93 resistivity measurement tests to be carried out.

The tables give the volume resistivity measured in ohm.cm, the surfaceresistivity measured in ohm/□; the tensile properties obtained are alsogiven.

All the tests are carried out at 23° C. The plaques are conditioned at50% humidity for 15 days before testing to measure surface resistivity.

EXAMPLES 1-6

a) Preparation of Compatibilizers C (Description of Operating Methodsfor the Synthesis of SM and SM/GMA)

Two jacketed steel reactors are used in cascade. The reactors areconnected by lagged pipework wrapped with trace-heating cable, avoidingany cooling during flow.

The styrene, the solvent, the initiator and the OH-TEMPO (a member ofthe nitroxide family) are introduced into the reactor at atmosphericpressure, then heated to 140° C. A kinetic study is carried out on thereaction mixture, and for this reason samples are taken from thejuncture when the temperature of the reaction mixture reaches about 130°C. All these samples are flash-evaporated (at 170° C. in an evacuatedbell jar) to determine the degree of conversion of styrene intopolystyrene. After about 60-70% of conversion into polystyrene, thepreheated methyl methacrylate is added, in one single addition, to theupper reactor at 100° C.

The reaction mixture is brought to about 140° C. during a period ofapproximately 3 hours, and then subjected to devolatilization so as toremove the volatile species. The copolymer is recovered in granule form.

The table below shows the amounts of reactants employed in the firststep of the synthesis for these two experiments. Synthesis of aSynthesis of a polystyrene-b- polystyrene-b- PMMA (PMMAgGMA) Ingredientsused (SM) (SM/GMA) Styrene in g 2850 2850 Ethylbenzene in g 500 500HO-TEMPO in g 3.51 3.51 Dicumyl peroxide in g 5.61 5.61 Methylmethacrylate in g 6650 6555 Glycidyl methacrylate 0 95 in g Styrenepolymerization 120 150 time in min Copolymerization time in 150 150 minExperimental Conditions:

Oil bath temperature: 160° C., condenser temperature: −20° C. The zeropoint for the time for styrene conversion is chosen when the temperatureof the polymerization mixture reaches 130° C.

The amount of MAM (or MAM/GMA mixture) is preheated to boiling beforebeing added to the reaction mixture. The oil bath temperature is keptconstant at 160° C. The condenser valve is in the closed position. Thetemperature becomes stable at 120° C. with an increase in the pressurein the reactor (P=1.5 bar) . The product is then recovered in granuleform. The product is analyzed by LAC, GPC and NMR and also by TEM once afilm has been obtained by slow evaporation in chloroform.

Supplementing these SEC analyses, quantitative LAC analyses were carriedout. Using this method, it was then possible to quantify the proportionsof homopolystyrene and of homoPMMA present in the reaction mixture, thento determine the composition by weight of the copolymers in terms ofpolystyrene and PMMA. Finally, an NMR analysis of the reaction mixturealso allowed us to determine the proportions of MMM, SMS and MMS triad,representative of a block copolymer or a random copolymer (MMM=threeadjacent MAM units, SMS=styrene unit followed by MAM, followed by S, andMMS=MAM unit followed by MAM, followed by styrene) . The determinationof this proportion allows the degree of structuring of the blockcopolymer to be characterized. A percentage of 100% of MMM triadindicates complete structuring.

All of the results are shown in the table below: SM SM/GMA Mw (g/mol)106 000 108 700 Mw/Mn 2.1 2 % PS gross (by weight) 61 65 % GMA 0 0.4 %by weight of homopolystyrene 29 30 % by weight of copolymer 71 70Average composition of PS/PMMA 45/55 copolymer % MMM triad 74

All of these results show that the products obtained are rich in blockcopolymers, since, simultaneously, the proportion of homopolystyrene isclose to 30%, there is no PMMA homopolymer and finally the proportion ofMMM triad is above 70%. Furthermore, the TEM analyses of these producesshow lamellar structures. Irrespective of the experiment, the structureobtained is always of lamellar type throughout its volume. It may benoted that the polystyrene lamellae are distended by homopolystyrene,since the thicknesses of these lamellae are greater than those of PMMA,although the composition of the copolymer is of the order of 50/50.

The polystyrene-block-PMMA block copolymer has a styrene content of 45%by weight and a MAM content of 55% by weight.

b) Preparation of Compositions by Mixing in an Extruder.

A twin-screw Werner and Pfleiderer extruder of 30 mm diameter is used,with a total throughput rate of 20 kg/h. This throughput rate representsthe total of the throughput rates for the ingredients used. Thetemperature settings for the barrels are from 230 to 250° C. The strandsdischarged from the machine are cooled in a water tank and granulated.These granules are injection-molded to give plaques, bars or dumb-bells,at similar temperatures (230-250° C.).

The results reported in the table above demonstrate the compatibilizingaction of the SM and SM/GMA block copolymers. The block copolymers wereused as obtained without separation from the homopolystyrene which wasmixed with them. This homopolystyrene may be considered as a styrenicresin (A). In the table of results below, the amounts of SM and SM/GMAindicated correspond to undiluted amounts of copolymer. The amounts ofhomopolystyrene introduced during the addition of block copolymer arereported in the second row of the table. Example No. 1 2 3 4 5 6 PS 4241100 90 88 88 86 86 Homopoly- 0.6 0.6 1.2 1.2 styrene MH 1657 10 10 10 1010 Poly- 1.4 2.8 styrene-b- PMMA Poly- 1.4 2.8 styrene-b- (PMMAgGMA) RvΩ · cm 1.40E+17 8.20E+13 2.50E+15 2.60E+15 2.50E+16 2.60E+15 Rs Ω/□2.30E+15 1.10E+12 3.70E+12 3.00E+12 1.10E+13 3.90E+12 Charpy notched ISO179:93 1eA +23° C. kJ/m² 11.1 7.1 8.6 11.1 10.9 11.1 Tensile fracture23° C. ISO 527:93-1B, v = 50 mm/min Sigma yield 27.4 24.4 25 25.5 25.826 (MPa) % yield 1.4 1.5 1.4 1.5 1.5 1.5 Sigma 22.7 17 19.4 21.9 22.122.4 fracture (MPa) % fracture 56.3 24.2 36.5 54.6 55.5 59

As can be seen, elongation at break and tensile strength are improved,while the impact properties of the matrix are retained and thecomposition is rendered antistatic.

The influence of the block copolymers is also visible at the particlesize level. For experiment 1, the size of the particles is of the orderof 1 μm, whereas for examples 5 and 6 it is reduced by half (0.5 μm).The reduction in the size of the particles is generally accompanied byan improvement in the compatibilizing action of the block copolymer.

1. A composition comprising, per 100 parts by weight: from 99 to 60parts by weight of a styrenic polymer (A), from 1 to 40 parts by weightof (B)+(C), (B) being a copolymer containing polyamide blocks andpolyether blocks comprising ethylene oxide units —(C₂H₄—O)—, and (C)being a compatibilizer selected from block copolymers comprising atleast one polymerized block comprising styrene and at least onepolymerized block comprising methyl methacrylate, the (B)/(C) ratio byweight being between 2 and
 10. 2. The composition as claimed in claim 1wherein the proportion of (B) is sufficient to give the finalcomposition a surface resistivity below 5.10¹³ Ω/□ measured to thestandard IEC93.
 3. The composition as claimed in claim 1 wherein theproportion of (B) is sufficient to give the final composition a volumeresistivity below 5.10¹⁶ Ω.cm measured to the standard IEC93.
 4. Thecomposition according to claim 1, wherein (A) comprises more than 50% ofstyrene.
 5. The composition as claimed in claim 1, wherein the amount of(C) is from 0.5 to 5 parts by weight in 100 parts by weight ofcomposition.
 6. The composition as claimed in claim 1, wherein thepolymerized block comprising styrene is present in C in a proportion offrom 20 to 80% by weight.
 7. The composition as claimed in claim 1,wherein the polymerized block comprising methyl methacrylate is presentin C in a proportion of from 20 to 80% by weight.
 8. The composition asclaimed in claim 1, wherein the polymerized block comprising styrenecomprises at least 50% by weight of styrene.
 9. The composition asclaimed in claim 1, wherein the polymerized block comprising styrenecomprises glycidyl methacrylate.
 10. The composition as claimed in claim1, wherein the polymerized block comprising methyl methacrylatecomprises more than 50% by weight of methyl methacrylate.
 11. Thecomposition as claimed in claim 1, wherein the polymerized blockcomprising methyl methacrylate comprises glycidyl methacrylate.
 12. Thecomposition as claimed in claim 1, wherein the block copolymer comprisesat least one polymerized block comprising styrene and at least onepolymerized block comprising methyl methacrylate being grafted withglycidyl methacrylate.
 13. The composition as claimed in claim 1,wherein (A) is a styrene-butadiene copolymer.
 14. The composition asclaimed in claim 1, wherein the amount of (B)+(C) is from 5 to 30 partsper 95-70 parts of (A).
 15. The composition as claimed in claim 1,wherein the amount of (B)+(C) is from 10 to 20 per 90-80 parts of (A).16. The composition as claimed in claim 1, wherein (C) is an S-B-Mtriblock copolymer, S representing the polymerized block comprisingstyrene, M representing the polymerized block comprising methylmethacrylate, and B representing an elastomeric block having a glasstransition temperature (Tg) below 5° C.
 17. An article manufactured froma composition as claimed in claim
 1. 18. A method for manufacturingelectronic components comprising utilizing the composition of claim 1.